1 /* Implements a string hashing function.
2 Copyright (C) 1995-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #ifdef HAVE_CONFIG_H
20 # include <config.h>
21 #endif
22
23 /* Specification. */
24 #include "hash-string.h"
25
26
27 /* Defines the so called `hashpjw' function by P.J. Weinberger
28 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
29 1986, 1987 Bell Telephone Laboratories, Inc.] */
30 unsigned long int
__hash_string(const char * str_param)31 __hash_string (const char *str_param)
32 {
33 unsigned long int hval, g;
34 const char *str = str_param;
35
36 /* Compute the hash value for the given string. */
37 hval = 0;
38 while (*str != '\0')
39 {
40 hval <<= 4;
41 hval += (unsigned char) *str++;
42 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
43 if (g != 0)
44 {
45 hval ^= g >> (HASHWORDBITS - 8);
46 hval ^= g;
47 }
48 }
49 return hval;
50 }
51